Assessment of the physical properties of laparoscopic myoma-fixation devices

Abstract

Background

The physical properties of three commercial 5-mm myoma-fixation devices available for clinical use (short-pitch corkscrew, long-pitch corkscrew, buttress-thread screw) and a standard wood screw were examined.

Methods

Fresh specimens of uterine leiomyoma masses were used to test the maximum traction force obtained from each device on 31 occasions. The myoma tissue at each traction site was evaluated histologically to determine its density. The maximal traction forces in each myoma density group were compared using a generalized estimating equations approach to linear regression based on repeated measures within each myoma. The bending strength also was determined for each device.

Results

A wide range of maximum traction forces with a mean of 130.8 ± 71.5 N (range, 21.6–341.6 N) over all devices and tissue densities was recorded. The mean maximum traction force provided by the short-pitch corkscrew (159.2 ± 12.2 N) was significantly higher (p < 0.01) than that of the other devices in medium-density myomas, and not significantly lower than that of other devices in low-density myomas. The mean maximum traction force provided by the buttress-thread screw was significantly lower than that of the short-pitch corkscrew only in medium density myomas, and did not differ significantly from that of the wood screw in any density group. The wood screw provided the highest bending strength (6.73 × 10⁴ N/m) (whereas the short- and long-pitch corkscrew provided the lowest (9.70 × 10² N/m and 1.95 × 10³ N/m, respectively) and the buttress-thread screw an intermediate (2.24 × 10⁴ N/m) strength (p < 0.0005 for all comparisons except for the two corkscrews).

Conclusions

Screw-type myoma-fixation devices can provide comparable traction force with high bending strength. A long-pitch corkscrew should not be used for laparoscopic myomectomy because of its low traction force and bending strength. When a commercial screw is not available, a standard wood screw can be used with acceptable traction force and very high strength for bending.